netdev - RE: Receiving of priority tagged packets

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Date:	Sun, 23 May 2010 03:51:41 -0700
From:	"Vladislav Zolotarov" <vladz@...adcom.com>
To:	"Eric Dumazet" <eric.dumazet@...il.com>
cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: Receiving of priority tagged packets



> -----Original Message-----
> From: netdev-owner@...r.kernel.org [mailto:netdev-owner@...r.kernel.org] On
> Behalf Of Vladislav Zolotarov
> Sent: Sunday, May 23, 2010 1:23 PM
> To: Eric Dumazet
> Cc: netdev@...r.kernel.org
> Subject: RE: Receiving of priority tagged packets
> 
> 
> > -----Original Message-----
> > From: Eric Dumazet [mailto:eric.dumazet@...il.com]
> > Sent: Sunday, May 23, 2010 1:07 PM
> > To: Vladislav Zolotarov
> > Cc: netdev@...r.kernel.org
> > Subject: Re: Receiving of priority tagged packets
> >
> > Le dimanche 23 mai 2010 à 02:36 -0700, Vladislav Zolotarov a écrit :
> > > Hello,
> > > We were playing with FCoE in our labs and saw the strange behavior of
> Linux
> > networking stack in regard to priority-tagged frames (the ones that have a
> > zero VID in a VLAN tag). We saw that until we explicitly added a zero vlan
> > interface (vconfig add ethX 0) the stack refused to accept such packets
> both
> > in HW VLAN acceleration mode (skb is indicated using
> > vlan_hwaccel_receive_skb()) and in a regular mode (skb is indicated with
> > netif_receive_skb()).
> > >
> > > However "IEEE Std 802.1Q, 2006 Edition DRAFT D0.1" in section 6.7 states
> > the following:
> > >
> > > Each Bridge Port shall support the following parameters for use by these
> > (EISS tagging and detagging) functions:
> > > 	c) an Acceptable Frame Types parameter with at least one of the
> > following values:
> > > 		1) Admit Only VLAN-tagged frames;
> > > 		2) Admit Only Untagged and Priority-tagged frames;
> > > 		3) Admit All frames
> > >
> > > So I guess this means that priority tagged frames should be accepted
> > together with the untagged frames on the default interface ethX.
> > >
> > > Could anyone explain, pls., what's the expected behavior of the Linux
> > Networking Stack in regard to the priority-tagged frames and what's
> expected
> > to be configured in order to start accepting them?
> > >
> > > Thanks in advance,
> > > vlad
> >
> > So if eth0.0 is setup, incoming vlanid=0 frames are delivered to eth0.0,
> > OK ? (This works in and out since commit 05423b241311c93)
> >
> > Now, if eth0.0 is not setup, you believe these frames should be directed
> > to eth0, as if they were not tagged ?
> >
> > That seems a bit strange.
> 
> Well, as far as I understood this is what IEEE 802.1Q spec states...

From the same spec:

***************
3.38 Priority-tagged frame: A tagged frame whose tag header carries priority information but carries no
VLAN identification information.
***************

Namely priority-tagged frames are frames that carry no VLAN identification information and namely should be treated as non-VLAN packets.

However, as u mentioned above, current Networking Stack implementation handles them as if they have VID 0.

These two are quite different ways to handle the frame, don’t u think?

> 
> >
> >
> >
> 
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